The present invention relates to a silent chain and, in particular, to the structure of a guide washer for a silent chain.
A silent chain is used conventionally as a power transmission chain. An example of a typical silent chain is shown in FIGS. 5 and 6. As shown in the figures, silent chain 100 is composed of multiple link plates 102, each having a pair of teeth 121 interleaved in the transverse and longitudinal directions. These link plates 102 are connected pivotally by a connecting pin, composed of a pair of long and short joint-pins 131 and rocker pin 132, which are inserted in pin aperture 122 of link plate 102. Guide link 104 is placed on the outside of outermost link plate 102. Both ends of joint pin 131 are fixed to the pin aperture in guide link 104. Rigidity of guide link 104 is higher in general than that of link plate 102.
A prestressing load is applied to the silent chain in general, after its assembly. When an excessive load such as a prestressing load is applied to a conventional silent chain, a shear load from the link plate acts on the center of the joint pin while the stretching of the aperture pitch of the guide row is restricted because both ends of the joint pin are fixed to a guide link of high rigidity. Thereby, the bending load acts on the joint pin and, as a result, the center portions of the joint pin and rocker pin can bend.
This invention addresses such a conventional situation and it offers a silent chain that minimizes bending of the connecting pin.
In one embodiment, the present invention comprises a silent chain in which a guide washer is provided to each connecting pin and the end of the joint pin is fixed to the pin aperture of the guide washer. Thereby, stretching of the aperture pitch of the guide row is not restricted, even when an excessive tensile load, such as a prestressing load is applied to the chain and the shear load from the link plates acts on the joint pin and no bending load acts on the joint pin, so that bending of the joint pin and rocker pin is minimized or prevented.
The total length of the rocker pin is equal to or longer than the total width of the interleaved link plates and is shorter than the distance between the guide washers opposing in the chain width direction. That is, in this case, attachment of the guide washer is not impeded even if the total length of the rocker pin is longer than the total width of the laminated link plates because the guide washer is independently provided to each connecting pin. Thereby, the tolerance on the length of the rocker pin can be large to ease dimensional control, and the effective cross-section of the connecting pin can be uniform across the total width of the link plates because the total length of the rocker pin is longer than the total width of the link plates.
In a conventional silent chain, the guide link has a pair of pin apertures on both of its sides (see FIGS. 5 and 6). Therefore, the total length of the rocker pin is preferably shorter than the total width of the laminated link plates to permit unforced attachment of the guide link, even when the length of the rocker pin in one pin aperture is different from another rocker pin in another pin aperture.
In this case, the two ends of the rocker pin must not be too deep in the pin apertures in the outermost link plate so that the total length of the rocker pin needs to be as close as possible to the total width of the link plates. Because of the above reason, tolerance on the length of the rocker pin in a conventional silent chain is tight and dimensional control is not easy.
In the present invention, the guide washer can have a blade spring portion. In this case, the elastic force of the blade spring acts in the chain width direction so that frictional force is generated between adjacent link plates in the chain width direction. As a result, the bending resistance of the chain increases and chordal vibration of the chain is suppressed.